As a method for manufacturing the color filter, a photolithography has been widely used for a long time. The photolithography is a method including: coating and drying a coloring photosensitive composition on a support to form a colored layer, then exposing and developing the colored layer to form a colored pixel of a first tint (for example, green), and forming a colored pixel of the remaining colors in the same manner.
However, as the pixels of a solid-state imaging device are micronized, it has become difficult to achieve both spectral characteristics and pattern formability of a color filter for the demand for micronization and thinning of the color filter in the pattern formation by a so-called photolithography. Specifically, in a color filter for a solid-state imaging device, the thickness thereof tends to become, for example, 1 μm or less for the thinning of a colored pattern and to become 2 or less (for example, 0.5 μm to 2.0 μm) for the pixel pattern size, thereby achieving a microsize.
In particular, as the thinning of a film progresses, the relative amount of colorants such as pigments in a film increases, while the amount of components other than the colorants, which contribute to the photolithographic properties, in a film relatively decreases, and the pattern formability due to the decrease has effects of improving the shape of a pattern observed on the top surface thereof even when a correction such as OPC is performed for the requirement of forming a pattern below 2.0 μm, but there is a problem such as insufficient rectangularity that the pattern edge of the pattern shape is round when observed the cross-section. It is known that in a color filter (a color filter manufactured by photolithography using a coloring radiation sensitive composition in which a pigment is dispersed in various compositions) using a pigment dispersion liquid, the rounding of the pattern edge become significant by influence of light scattering by the pigment when exposuring.
In particular, recently, due to the demand for the higher definition of the color filter for a solid-state imaging device, the formability of a pattern of, for example, 1.4 μm becomes problematic, and thus, the resolution may almost reach a limit in the photolithography in the related art.
For a method for manufacturing a color filter using the photolithography, a processing method using dry etching has been suggested as a method effective to realize micronization and thinning of a pattern. The dry etching has been adopted in the related art as a method for forming a pattern (each colored pixel) in a rectangular form, and a method for forming a pattern which combines the photolithography and the dry etching have been suggested (see, for example, Patent Documents Japanese Patent Application Laid-Open No. 2006-222290 and Japanese Patent Application Laid-Open No. 2007-48774).
Recently, in order to improve the device performance of a solid-state imaging device such as an image sensor having a color filter, a pattern forming method has been attempted, which combines patterning of the color filter by dry etching and a planarization treatment by an etch-back treatment or a polishing treatment such as chemical mechanical polishing (CMP) treatment in the device preparation process. Specific examples thereof include a method, including: using a first colored pattern formed by patterning a first colored layer by dry etching as a template, stacking a second colored layer so as to cover the first colored pattern, and then subjecting the second colored layer to planarization treatment until the first colored layer is at least exposed.
However, in the related art, there was a problem in that the pattern in the first colored pattern used as a template has insufficient rectangularity. In addition, in the planarization treatment subsequent to the dry etching, there was a problem in that the surface of the colored pattern becomes rough.
The present invention has been made in consideration of the above-described problems, that is, an object of the present invention is to provide a method for manufacturing a color filter which combines patterning of the color filter by dry etching and planarization treatment, wherein the rectangularity of the pattern in the first colored pattern is high and the surface of the colored pattern may be suppressed from being roughened during the planarization treatment, a color filter and a solid-state imaging device.